Wetland Delineation for the 53 rd Street Overpass Project Corvallis, Oregon

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1 Wetland Delineation for the 53 rd Street Overpass Project (Township 12 South, Range 5 West, Section 4 West end of Tax Lot 120 & north side of Union Pacific right-of-way) Prepared for Benton County Public Works 360 SW Avery Avenue Corvallis, OR March 30, 2009

2 TABLE OF CONTENTS Page 1. INTRODUCTION 1 2. RESULTS AND DISCUSSION 1 A. Landscape Setting and Land Use 1 B. Site Alterations 1 C. Precipitation Data and Analysis 1 D. Methods 2 E. Description of All Wetlands and Other Non-wetland Waters 3 F. Deviation from LWI or NWI 4 G. Mapping Method 4 H. Additional Information 4 I. Results and Conclusions 4 J. Disclaimer 4 APPENDIX A: Figures Figure 1: Vicinity Map Figure 2: Tax Lot Map Figure 3: City of Corvallis Local Wetland Inventory Map Figure 4: Soil Survey Map Figure 5(a-d): Aerial Photos: 2007, 2000, 1994 & 1959 Figure 6 (a-c): Potentially Jurisdictional Wetlands within Study Area APPENDIX B: APPENDIX C: APPENDIX D: Wetland Delineation Data Sheets Site Photographs (ground level) Literature Citations

3 A. INTRODUCTION Benton County Public Works staff conducted a wetland delineation within the subject property in preparation of developing plans to construct a railroad overpass on 53 rd Street. The current 53 rd Street alignment has sight visibility and traffic safety issues due to an existing railroad crossing underpass and a trestle support that is located in the middle of 53rd Street. In addition, the railroad underpass becomes periodically inundated during high rainfall events as the culvert under 53 rd Street that conveys Dunawi Creek is undersized to adequately convey larger storm events (>10- year storm events). Traffic on 53 rd Street exceeds the present road capacity. The proposed overpass would not only provide capacity to meet the Corvallis Metropolitan Area s future traffic needs, but also would eliminate the public safety issue when 53 rd Street becomes inundated during storm events. The bridge/overpass would also eliminate the final fish passage barrier that exists in upper Dunawi Creek as it is proposed that the culverts at the railroad trestle and 53 rd Street would be removed and an open stream channel would be restored. B. RESULTS AND DISCUSSION A. Landscape Setting and Land Use The project is on the west edge of the City of Corvallis and is located on a broad, flat terrace in the Willamette Valley below Bald Hill and the first hills to the Coast Range. It is located in the Dunawi Creek watershed in the Mary s River sub-basin. For the past 50+ years the land has been in agricultural production; first pasture land, then Christmas tree farm. Historically, the area was likely wet prairie, common to this area in the mid-willamette Valley. The study area for this project is located on the western ¼ of tax lot #120 and the north side of the Union Pacific Railroad right-of-way. B. Site Alterations Based upon an examination of historical aerial photographs from 1959 to 2007 (Figures 5a-d), the majority of the site alterations that have occurred in the study area appear to have been related to agricultural practices. It is evident that Dunawi Creek has been ditched and straightened prior to In the late 1990 s a Christmas tree farm/nursery was attempted on the far western ¼ of the property presumably where the soils drained well enough to support trees intolerant of saturated soil conditions. Trees planted included Douglas fir, ponderosa pine and yellow cedar. Since that time it appears the tree farm operation has suspended and the trees have grown out out of the stage whereby they could be used for their intended purpose. Neither onsite conditions nor historical aerial photographs suggest that the study area has ever been artificially drained using drainage tile. C. Precipitation Data and Analysis The wetlands within the Study Area were delineated March 4 & 5, Precipitation recorded on those dates was 0.09 inches and 0.30 inches respectively. Recorded precipitation for the two week period prior to March 4 was 3.27 inches. Total precipitation for the water year to date was inches which is 68% of normal

4 Table 1. Shows the average monthly precipitation in Corvallis for the three months prior to the March 4 & 5 site visit. Precipitation for those months is considered below average for the area (NRCS WETS table for Corvallis, 2002). Table 1 also shows the recorded rainfall for Corvallis three months prior to the delineation. Table 1. Average Monthly Precipitation (NRCS WETS Table) Month Average* 30% chance will have Observed Precipitation** Less Than More Than December, January, February, *Average Monthly Rainfall (NRCS WETS Table) ** Recorded Monthly Rainfall (Weather Underground) for Corvallis Recorded precipitation for the December through February period was below average for each month. Although there is a precipitation deficit in the months preceding the March delineation it is not expected to have significant effect on the wetland boundaries because the evidence of hydrology included hydric soils, geomorphic position of the wetland and secondary hydrologic indicators. Wetlands were saturated within the upper 12 inches of the soil profile at the time of the delineation. Areas where primary indicators of hydrology were absent, secondary indicators of hydrology were used, in conjunction with hydrophytic vegetation and hydric soils, to determine the wetland boundary. A. Methods Benton County staff delineated the limits of the wetlands within the study area based on the presence of wetland hydrology, hydric soils, and hydrophytic vegetation, in accordance with the Routine On-site Determination, as described in the Corps of Engineers Wetland Delineation Manual, Wetlands Research Program Technical Report Y-87-1 ( The 1987 Manual ) and the Interim Regional Supplement for Western Mountains, Valleys, and Coast Region ( The Supplement ). Potential wetlands were identified prior to the field investigation using the US Geological Survey (USGS) 7.5 minute topographic quadrangle maps (USGS, 1985), the Soil Survey of Benton County, Oregon (1975) and the City of Corvallis Local Wetland Inventory (LWI) (Pacific Habitat Services, 2004). Wetland delineation data forms provided by the Oregon Department of State Lands (DSL) were used to record soils, vegetation, and hydrology data at 40 plots within the Study Area. Plots were typically paired to include a representative sample of each wetland and adjacent non-wetland. Paired plots were located where distinct changes in vegetation community, topography, soils, and hydrological characteristics occurred along the wetland/upland boundary to substantiate the wetland boundary location

5 B. Description of all Wetlands and Other Non-Wetland Waters Within the Study Area boundaries 2 wetlands, Dunawi Creek and an un-named tributary to Dunawi Creek was identified and described below: Wetland A Within the Study Area, Wetland A is 1.07 acres in size. Wetland A is located north of the Union Pacific Railroad and south of T11S, R5W Section 33 #300. Wetland A is a depression wetland under the HGM class & a palustrine forested (PFO) wetland under the Cowardin classification system. Dominant plant species within Wetland A include Oregon ash and equisetum, while dominant plant species within the adjacent upland area include Himalayan blackberry. This wetland continues north of the study area and was mapped as part of the wetland delineation DSL #WD and Corps #NWP /1. Wetland B Within the Study Area, Wetland B is 9.02 acres in size. Wetland B is located south of the Union Pacific Railroad. Dunawi Creek flows through the northern 1/3 of the wetland delineated. Hydrologic sources of this wetland is varied; including overbank flooding from Dunawi Creek, seasonal perched water tables due to relatively impermeable subsoils and overland flow of surface water from sources off-site and upslope. The wetland continues east of the study area and becomes an expansive wetland system integrated with the Dunawi Creek watershed. Under the HGM classification system the wetland varies from riverine flow-through to flats depending upon the location of the wetland and proximity to the creek. Under the Cowardin classification system (where vegetation has not been managed/manipulated within the past 10 years) most of the wetlands would be considered palustrine emergent meadow PEM). Dunawi Creek Dunawi Creek flows south-easterly through the site, entering the study area from a 60 culvert under the present 53 rd Street and flows out of the Study Area. Dunawi Creek is likely a perennial stream at this location and Ordinary High Water (OHW) of the creek averages wide through the study area. The stream is incised and the bed and bank consists of fine sediment and silty clay. Riparian vegetation along the creek is a mature forest where Oregon ash and black cottonwood predominate. Pacific willow and Himalayan blackberry compose the majority of understory vegetation. Un-named Tributary to Dunawi Creek An un-named tributary to Dunawi Creek flows from a 42 culvert under SW Cherry Avenue and 53 rd Street on the western edge of the Study Area adjacent to 53 rd Street and flows north to its confluence with Dunawi Creek. The tributary is 3 feet wide on average at Ordinary High Water (OHW) and had flowing water during the time of the field delineation. There are no adjacent wetlands outside the tributary. The tributary is incised and follows along 53 rd Street. The boundary for this drainage was determined by a clear hydrologic break between the drainage and adjacent upland and the abrupt change in vegetation from hydrophytic vegetation in and alongside the drainage to upland vegetation outside the area of hydrologic influence. Source of hydrology appears to be area drainage as this tributary likely was piped or tiled when the residential development west of 53 rd Street was constructed over 30 years ago

6 C. Deviation from LWI or NWI The NWI map of this area does not indicate any wetlands (excepting Dunawi Creek), not unusual because NWI maps are generated primarily through the interpretation of color infrared aerial photographs (scale of 1:58,000) with limited ground truthing to confirm the interpretations. Often, smaller wetlands or areas obscured by vegetation are missed. The Corvallis Local Wetland Inventory (LWI) identifies a band of wetland in close association with Dunawi Creek over 100 feet wide. The limits of the LWI boundary correspond generally with the portion of the wetlands onsite that could be considered riverine flow-through by HGM classification and PFO by Cowardin classification. However, the wetland boundaries as mapped by Benton County staff extend far beyond the limits of the LWI. D. Mapping Method Benton County staff flagged the limits of the wetlands within the study area with pink ribbon. Test pits were located and flagged using orange pin flags marked Benton County #. Benton County Engineering Department performed professional land survey using Leica total stations with Trimble Onboard software. The accuracy of the survey is sub-centimeter. None. E. Additional Information F. Results and Conclusions Within the Study Area, Benton County delineated 2 potentially jurisdictional wetlands, Dunawi Creek and an un-named tributary to Dunawi Creek. The total area of wetlands, Dunawi Creek and the un-named tributary are summarized in the following table: Table 2. Total wetland and other waters within the 53 rd Street Overpass Study Area in west Water Feature Area (Acres) HGM Class Cowardin Class Wetland A 1.07 Dep. PFO Wetland B 9.02 RFT, Flats PFO, PEM Dunawi Creek 0.30 RFT PFO, PSS Un-named Tributary 0.08 RFT PSS G. Required Disclaimer This report documents the investigation, best professional judgment and conclusions of the investigator. It is correct and complete to the best of our knowledge. It should be considered a Preliminary Jurisdictional Determination of wetlands and other waters and used at your own risk unless it has been reviewed and approved in writing by the Oregon Department of State Lands in accordance with OAR through

7 APPENDIX A (Maps & Figures)

8 APPENDIX B (Data Sheets)

9 APPENDIX C (Site Photographs)

10 Benton County Public Works Wetland Delineation for 53rd Street Overpass Photo Point A: View of Wetland B looking northeast Photo Point B: Example of Wetland Hydrology (ant hills) within planted Christmas tree farm (douglas fir)

11 Benton County Public Works Wetland Delineation for 53rd Street Overpass Photo Point C: View of wetland/upland boundary; wetland B looking east Photo Point D: Un-named tributary to Dunawi Creek

12 Benton County Public Works Wetland Delineation for 53rd Street Overpass Photo Point E: Confluence of Un-named tributary with Dunawi Creek at 53rd Street Culvert Photo Point F: View of Dunawi Creek looking downstream; creek is 18 wide at OHW

13 APPENDIX D (Literature Citations)

14 Cooke, Sarah Spear A Field Guide to the Common Wetland Plants of Western Washington and Northwestern Oregon. Seattle Audubon Society, Seattle, WA Corvallis Local Wetland Inventory Pacific Habitat Services. %20Ordinance%20Exhibit%20A/Map-RiparianCorridorsAndWetlands18x30.pdf Cowardin, L.M., Carter, V., Golet, F.C., and E.T. LaRoe Classification of Wetlands and Deepwater Habitats of the United States. Washington, D.C.: Government Printing Office. Environmental Laboratory Corps of Engineers Wetlands Delineation Manual. Technical Report Y-87-1, US Army Engineer Waterways Experiment Station, Vicksburg, MS Environmental Laboratory US Army Corps of Engineers Interim Regional Supplement to the Corps Delineation Manual: Western Mountains, Valleys, and Coast Range. Technical Report ERDC/EL TR US Army Corps of Engineers Research and Development Environmental Laboratory, Vicksburg, MS Guard, Jennifer Wetland Plants of Oregon and Washington. Lone Pine Publishing, Redmond, WA Hitchcock, C. Leo, and Arthur Cronquist Flora of the Pacific Northwest. University of Washington Press, Seattle, WA Munsell Color Charts Munsell Soil Color Charts, 2000 Edition. Baltimore, MD Oregon Department of State Lands, 2008, Wetland Delineation Checklist; USDA Natural Resources Conservation Services WETS Table Documentation National Water and Climate Center, Portland, OR Oregon WETS tables ftp by NRCS County Number ftp://ftp.wcc.nrcs.usda.gov/support/climate/wetlands/or/ USDA Natural Resources Conservation Service Oregon Hydric Soils List USDA Natural Resource Conservation Service Soil Survey of Benton County USGS US Geological Survey Corvallis. 7.5 Minute